release: add step to publish GitHub security advisory (#6929)

.github/ISSUE_TEMPLATE/dev_release_minor_version.md

@@ -43,6 +43,7 @@ On the release branch:
 
 On the `main` branch:
 
+- [ ] Publish [GitHub security advisories](https://github.com/gogs/gogs/security) for security patches included in the release.
 - [ ] Update the repository mirror on [Gitee](https://gitee.com/unknwon/gogs).
 - [ ] Create a new release announcement in [Discussions](https://github.com/gogs/gogs/discussions/categories/announcements).
 - [ ] Send a tweet on the [official Twitter account](https://twitter.com/GogsHQ) for the minor release.

.github/ISSUE_TEMPLATE/dev_release_patch_version.md

@@ -47,6 +47,7 @@ On the release branch:
 
 On the `main` branch:
 
+- [ ] Publish [GitHub security advisories](https://github.com/gogs/gogs/security) for security patches included in the release.
 - [ ] Post the following message on issues that are included in the patch milestone:
     ```
     The <MAJOR>.<MINOR>.<PATCH> has been released that includes the patch of the reported issue.